Negative c-plate type optical anisotropic film comprising poly cycloolefin and method for preparing the same

ABSTRACT

The present invention provides a negative C-plate type optical anisotropic film having negative birefringence along the thickness direction. In particular, the present invention provides n film comprising cycloolefin addition polymer, which is prepared by addition polymerizing norbornene-based monomers, a method for preparing the same, and a liquid crystal display comprising the same. The film of the present invention can be used for optical compensation films of a variety of LCD (liquid crystal display) modes because the refractive index alone the thickness direction can be controlled by the kind and amount of functional groups introduced to the cycloolefin addition polymer.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an optical film prepared from apolycycloolefin, and more particularly to an opticalanisotropic-compensation film comprising a polycycloolefin, havingnegative birefringence along the thickness direction (n_(x)≈n_(y)>n_(z);n_(x)=refractive index along the slow axis; n_(y)=refractive index alongthe fast axis; n_(y)=refractive index along the fast axis;n_(z)=refractive index along the thickness direction), and a method forpreparing the same.

(b) Description of the Related Art

Use of liquid crystal displays (LCDs) is on the rapid increase, sincethey consume less power and are, thereby capable of running for hoursusing a battery, they save space, and are more lightweight than cathoderay tube (CRT) displays. Recently, use of medium-to-large sized LCDs hasbeen on the increase in computer monitors and TVs. Particularly, inmedium-to-large sized LCDs, it is important to offer good image qualityover a wide view angle and to improve contrast when the driving cell isturned ON/OFF.

For this reason, a variety of liquid crystal mode displays, such as dualdomain TN, ASM (axially symmetric aligned microcell), VA (verticalalignment), SE (surrounding electrode), PVA (patterned VA), and IPS(in-plane switching), have been developed. Each of these modes has itsown liquid crystal arrangement and unique optical anisotropy.Accordingly, a variety of compensation films are required to compensatefor the linearly polarized light's change in the optical axis due to theoptical anisotropy of liquid crystals in LCDs.

The compensation film plays an important role in solving light leakageof the vertical polarizing element at about 45° from the optical axis,as well as in optically compensating the optical anisotropy of liquidcrystals in LCDs. Therefore, development of an optical film capable ofaccurately and effectively controlling the optical anisotropy is themost important factor for optical compensation of a variety of liquidcrystal display modes.

The optical anisotropy is expressed in R_(th), which is the phasedifference along the fast axis (y-axis) and along the thicknessdirection (z-axis), and R_(e), which is the in-plane phase difference,as shown in the following Equation 1 and Equation 2:R _(th)=Δ(n _(y) −n _(z))×d  Equation 1R _(e)=Δ(n _(x) −n _(y))×d  Equation 2

In Equations 1 and 2,

-   -   n_(x) is the in-plane refractive index along the machine        direction or along the slow axis (x-axis), n_(y) is the in-plane        refractive index along the transverse direction or along the        fast axis (y-axis), n_(z) is the refractive index along the        thickness direction (z-axis), and d is the film thickness.

If any of R_(th) or R_(e) is much larger than the other, the film can beused as a compensation film having uni-axial optical anisotropy, and ifboth of them are not close to 0, the film can be used as a compensationfilm having bi-axial optical anisotropy.

Compensation films having uni-axial optical anisotropy can be classifiedinto the A-plate (n_(x)≠n_(y)≈n_(z)) and the C-plate(n_(x)≈n_(y)≠n_(z)). The in-plane phase difference can be controlled bysuch secondary film processing as precise film stretching, and thusoptical isotropic materials can be uni-axial oriented. However, thecontrolling optical anisotropy along the thickness direction bysecondary processing is relatively limited, and it is preferable to usea transparent polymer material having different molecular arrangementsalong the thickness direction and the planar direction. In particular,when considering compensation along the optical axis only, an idealcompensation film should have an optical axis which is a mirror image ofthat of the liquid crystal layer, and thus the negative C-plate havingnegative birefringence along the thickness direction can be required forVA mode and TN mode, which have higher refractive indices along thethickness direction than the planar direction.

Because the negative C-plate has a very small R_(e) value, R_(th) can beobtained from the following Equation 3 by measuring R_(θ), which isexpressed by the product of optical path length and Δ(n_(y)−n_(θ)), thedifference of refractive index along the fast axis and refractive indexwhen the angle between the film plane and the incident ray of light islarge: $\begin{matrix}{R_{th} = \frac{R_{\theta} \times \cos\quad\theta_{f}}{\sin^{2}\theta_{f}}} & {{Equation}\quad 3}\end{matrix}$

In Equation 3, θ_(f) is the internal angle.

For polymer materials that can be used as the negative C-plate, adiscotic liquid crystal (e.g., U.S. Pat. No. 5,583,679), a polyimidehaving a planar phenyl group at the main chain (e.g., U.S. Pat. No.5,344,916), and a cellulosic film (e.g., WO 2000/55657) are disclosed.

Of these materials, the discotic liquid crystal cannot be used alone andrequires precise coating of up to several micrometers thickness on atransparent support. In addition to the cost of the coating process, therelative large birefringence of the discotic liquid crystal results in arelatively large phase difference as a result of a small difference incoating thickness, and pollutants such as dust remaining on the coatingfilm surface or in the discotic liquid crystal solution may causeoptical defects.

The polyimide is problematic because it experiences optical loss as itabsorbs light in the visible region, and it peels easily due to weakadhesivity and high water absorptivity.

The cellulose ester-based film has problems in dimensional stability andadhesivity due to high water absorptivity, and is disadvantageous indurability compared with cycloolefin polymers due to the relatively highcontent of phase retarder compound having a low molecular weight. Also,resins comprising such an aromatic phase retarder compound have arelatively large wavelength dispersive characteristic due to theabsorption in the visible region, which is seen from Sellmeyer's formulaexpressed by the following Equation 4: $\begin{matrix}{{n^{2}(\lambda)} = {1 + \frac{A_{1}\lambda^{2}}{\lambda^{2} - \lambda_{1}^{2}} + \frac{A_{2}\lambda^{2}}{\lambda^{2} - \lambda_{2}^{2}} + \ldots}} & {{Equation}\quad 4}\end{matrix}$

In Equation 4,

-   -   n is the refractive index, λ₁, λ₂, . . . are absorption        wavelengths, and A₁, A₂, . . . are fitting parameters.

Therefore, for a polymer material comprising an aromatic compound thatis to be used as a compensation film, compensation of the wavelengthdispersive characteristic should be considered because the phasedifference varies a lot depending on the wavelength. That is, even if acompensation film comprising such material is optimized for opticalcompensation near 550 nm, where the highest optical efficiency isobtained, there arises a coloration problem because optical compensationis not satisfied for other wavelengths. This problem makes it difficultto control the display color.

On the contrary, since a cycloolefinic polymer does not absorb light inthe visible region, it has a flat wavelength dispersive characteristic,and thus results in small phase differences with respect to wavelength.Cycloolefinic copolymers are well known in the literature. They have lowdielectric constants, and low water absorptivity due to high hydrocarboncontent.

For methods of polymerizing a cyclic monomer, there are ROMP (ringopening metathesis polymerization), HROMP (ring opening metathesispolymerization followed by hydrogenation), copolymerization withethylene, and homogeneous polymerization, as seen in the followingScheme 1. Scheme 1 shows polymers having different structures andphysical properties that are obtained from the same monomers dependingon which polymerization method is applied.

The polymer obtained by ROMP has poor heat stability and oxidativestability due to unsaturation of the main chain, and is used as athermoplastic resin or thermosetting resin. But the resin prepared fromthis method has a heat stability problem. Hydrogenation generallyincreases the glass transition temperature of the ROMP polymer by some50° C., but the glass transition temperature is still low due to theethylene group present between the cyclic monomers (Metcon 99).

In addition, cost increases due to more synthesis steps and weakmechanical properties are barriers to commercial utilization of suchpolymers. It has been reported that a polymer having a large molecularweight but a narrow molecular weight distribution can be obtained if azirconium-based metallocene catalyst is used (Plastic News, Feb. 27,1995, p.24). However, the activity decreases as the cyclic monomerconcentration increases, and the copolymer has a low glass transitiontemperature (T_(g)<200° C.). Also, although the heat stability isimproved, the mechanical strength is weak and chemical resistanceagainst solvents or halogenated hydrocarbons is not good.

A cycloolefinic polymer obtained by addition polymerization using ahomogeneous catalyst has a rigid and bulky ring structure in everymonomer unit of the main chain. Thus, the polymer has very high T_(g),and is amorphous. Therefore, the polymer neither experiences opticalloss due to scattering nor absorbs light in the visible region byπ-conjugation. Particularly, a cycloolefinic polymer having a relativelylarge molecular weight, which is obtained by addition polymerizationusing an organometallic compound as a catalyst, is electricallyisotropic and has a low dielectric constant (J. Appl. Polym. Sci. Vol.80, p 2328, 2001).

Thus, polymers prepared using norbornene monomers have hightransmittivity, low birefringence, and high T_(g), so they can be usedfor optical purposes such as in light guide panels and optical discs.Also, due to low dielectric constants, superior adhesivity, electricalisotropy, and high T_(g), they can be used as insulation materials.

Introduction of substituents to a polymer comprising hydrocarbons is auseful method to control chemical and physical properties of thepolymer. However, when introducing a substituent having a polarfunctional group, a free electron pair of the polar functional grouptends to react with the active catalytic site and functions as acatalyst poison. Therefore, it is not always easy to introduce a polarfunctional group to a polymer, and there is a limit to the kind andamount of substituents that can be introduced. It is known that polymersprepared from substituted cyclic monomers have small molecular weights.In general, norbornene-based polymers are prepared by usingpost-transition organometallic catalysts. Most of such catalysts showlow activity in polymerization of monomers containing polar groups, andgenerally, the prepared polymers have molecular weights of not more than10,000 (Risse et al., Macromolecules, 1996, Vol. 29, 2755-2763; Risse etal., Makromol. Chem., 1992, Vol. 193, 2915-2927; Sen et al.,Organometallics 2001, Vol 20, 2802-2812; Goodall et al., U.S. Pat. No.5,705,503).

SUMMARY OF THE INVENTION

An object of the present invention is to solve the problems describedabove and to provide an optical anisotropic film comprising acycloolefinic polymer having negative birefringence along the thicknessdirection, which requires no coating process and experiences no opticalloss due to light absorption in the visible region.

Another object of the present invention is to provide a method forpreparing an optical anisotropic film, a birefringence of which alongthe thickness direction can be controlled by the kind and content of afunctional group introduced to the cycloolefin.

Still another object of the present invention is to provide an opticalanisotropic film having superior water absorption resistance anddurability and small birefringence difference with respect towavelength, and a method for preparing the same.

Still another object of the present invention is to provide a liquidcrystal display comprising an optical compensation film comprising acycloolefinic polymer having negative birefringence along the thicknessdirection, which requires no coating process and experiences no opticalloss due to light absorption in the visible region.

To attain the objects, the present invention provides a negative C-platetype optical anisotropic film comprising a polycycloolefin.

The present invention also provides an optically anisotropic transparentfilm with a retardation value (R_(th)) defined by the following Equation1 being 30 to 1000 nm, and a phase difference ratio for two wavelengthsat a given declined angle being (R₄₅₀/R₅₅₀)=1 to 1.05 and(R₆₅₀/R₅₅₀)=0.95 to 1, respectively, wherein R₄₅₀ is the phasedifference at wavelength=450 nm, R₅₅₀ is the phase difference atwavelength=550 nm, and R₆₅₀ is the phase difference at wavelength=650nm:R _(th)=Δ(n _(y) −n _(z))×d  Equation 1

In Equation 1,

-   -   n_(y) is the in-plane refractive index along the transverse        direction or along the fast axis measured at the wavelength of        550 nm;    -   n_(z) is the refractive index along the thickness direction        (z-axis) measured at the wavelength of 550 nm; and    -   d is the film thickness.

The present invention also provides an optical anisotropic compensationfilm comprising a polycycloolefin for use in a liquid crystal display.

Further, the present invention provides a method for preparing anegative C-plate type optical anisotropic film comprising apolycycloolefin, which comprises the steps of:

-   -   a) addition polymerizing norbornene-based monomers to prepare a        norbornene-based addition polymer;    -   b) dissolving said norbornene-based addition polymer in a        solvent to prepare a norbornene-based addition polymer solution;        and    -   c) coating or casting said norbornene-based addition polymer        solution on a plate and drying the same.

Further, the present invention provides a liquid crystal displaycomprising a negative C-plate type optical anisotropic film comprising apolycycloolefin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention is described in more detail.

The present invention provides a negative C-plate type opticalanisotropic film, particularly a film comprising a cycloolefin additionpolymer prepared from addition polymerization of a norbornene-basedmonomer, a method for preparing the same, and a liquid crystal displaycomprising the same.

The cycloolefin addition polymer of the present invention, which isprepared from addition polymerization of a norbornene-based monomer,includes a homopolymer prepared from addition polymerization ofnorbornene-based monomers represented by the following Chemical Formula1, and a copolymer prepared from addition copolymerization with anothermonomer:

In Chemical Formula 1,

-   -   m is an integer from 0 to 4;    -   R₁, R₂, R₃, and R₄ are independently or simultaneously hydrogen;        a halogen; a C₁ to C₂₀ linear or branched alkyl, alkenyl, or        vinyl; a C₄ to C₁₂ cycloalkyl substituted by a hydrocarbon or        unsubstituted; a C₆ to C₄₀ aryl substituted by a hydrocarbon or        unsubstituted; a C₇ to C₁₅ aralkyl substituted by a hydrocarbon        or unsubstituted; a C₃ to C₂₀ alkynyl; a C₁ to C₂₀ linear or        branched haloalkyl, haloalkenyl, or halovinyl; a C₅ to C₁₂        halocycloalkyl substituted by a hydrocarbon or unsubstituted; a        C₆ to C₄₀ haloaryl substituted by a hydrocarbon or        unsubstituted; a C₇ to C₁₅ haloaralkyl substituted by a        hydrocarbon or unsubstituted; a C₃ to C₂₀ haloalkynyl; or a        non-hydrocarbonaceous polar group containing at least one of        oxygen, nitrogen, phosphorus, sulfur, silicon, or boron; and    -   if R₁, R₂, R₃, and R₄ are not hydrogen, a halogen, or a polar        functional group, R₁ and R₂, or R₃ and R₄ may be connected to        each other to form a C, to C₁₀ alkylidene group, or R₁ or R₂ may        be connected to R₃ or R₄ to form a C₄ to C₁₂ saturated or        unsaturated cyclic group or a C₆ to C₂₄ aromatic cyclic        compound.

Said non-hydrocarbonaceous polar group can be selected from thefollowing functional groups, but is not limited to them:

Each R₅ of said non-hydrocarbonaceous polar group is a C₁ to C₂₀ linearor branched alkyl, haloalkyl, alkenyl, haloalkenyl, vinyl, or halovinyl;a C₄ to C₁₂ cycloalkyl or halocycloalkyl substituted by a hydrocarbon orunsubstituted; a C₆ to C₄₀ aryl or haloaryl substituted by a hydrocarbonor unsubstituted; a C₇ to C₁₅ aralkyl or haloaralkyl substituted by ahydrocarbon or unsubstituted; or a C₃ to C₂₀ alkynyl or haloalkynyl;

-   -   each of R₆, R₇, and R₈ is hydrogen; a halogen; a C₁ to C₂₀        linear or branched alkyl, haloalkyl, alkenyl, haloalkenyl,        vinyl, halovinyl, alkoxy, haloalkoxy, carbonyloxy, or        halocarbonyloxy; a C₄ to C₁₂ cycloalkyl or halocycloalkyl        substituted by a hydrocarbon or unsubstituted; a C₆ to C₄₀ aryl,        haloaryl, aryloxy, or haloaryloxy substituted by a hydrocarbon        or unsubstituted; a C₇ to C₁₅ aralkyl or haloaralkyl substituted        by hydrocarbon or unsubstituted; or C₃ to C₂₀ alkynyl or        haloalkynyl; and    -   p is an integer from 1 to 10.

The norbornene-based monomer of the present invention is a monomercomprising at least one norbornene(bicyclo[2,2,1]hept-2-ene) unitrepresented by the following Chemical Formula 2:

The negative C-plate type optical anisotropic film of the presentinvention can be prepared from any cycloolefinic polymer obtained fromaddition polymerization of a norbornene-based monomer. A variety ofcycloolefinic polymers can be obtained depending on which catalystsystem is selected during the addition polymerization. For example, ahomopolymer of norbornene-based monomers containing nonpolar functionalgroups, a copolymer of norbornene-based monomers containing differentnonpolar functional groups, a homopolymer of norbornene-based monomerscontaining polar functional groups, a copolymer of norbornene-basedmonomers containing different polar functional groups, or a copolymer ofnorbornene-based monomers containing nonpolar functional groups andnorbornene-based monomers containing polar functional groups can beprepared. In particular, it is preferable that the norbornene-basedpolymer preferably contains polar groups and has a number-averagemolecular weight at least 10,000. As in common polymerization, theaddition polymerization is performed by mixing monomers and a catalystin a solvent.

These cycloolefinic polymers may contain any polar group regardless ofthe catalyst system. By changing the kind and content of the polarfunctional groups or nonpolar functional groups, the optical anisotropyof the polymers can be altered. The resultant polymers can be used incompensation films for LCDs.

A polycycloolefin containing polar groups can be prepared by a varietyof methods. Particularly, it is preferable to obtain it from additionpolymerization of norbornene-based monomers in the presence of a group10 transition metal catalyst.

More preferably, a catalyst system comprising a group 10 transitionmetal compound catalyst, an organic compound cocatalyst comprising agroup 15 element which has lone pair electrons that function as electrondonors, and a salt cocatalyst comprising a group 13 element which can beweakly coordinated to said transition metal, are contacted withnorbornene-based monomers represented by Chemical Formula 1 to preparepolar group-substituted cycloolefinic polymers having large molecularweights with a high yield.

When preparing a cycloolefinic polymer containing such polar groups asester groups or acetyl groups, it is preferable to contact a catalystsystem comprising:

-   -   i) a group 10 transition metal compound;    -   ii) a compound comprising a neutral group 15 electron donor        ligand, a cone angle of which is at least 160°; and    -   iii) a salt capable of offering an anion which can be weakly        coordinated to said transition metal of i)    -   with norbornene-based monomers represented by Chemical Formula        1, which contain such polar functional groups as ester groups or        acetyl groups. However, cycloolefinic polymers containing polar        functional groups and method for preparing the same are not        limited to the aforementioned.

Preferably, the group 10 transition metal of i) is a compoundrepresented by the following Chemical Formula 3 or Chemical Formula 4:M(R)(R′)  Chemical Formula 3

In Chemical Formula 3 and Chemical Formula 4,

-   -   M is a group 10 metal; and    -   each of R and R′ is an anion-leaving group that can be easily        removed by an weakly coordinating anion, which can be selected        from the group consisting of a hydrocarbyl, a halogen, a        nitrate, an acetate, trifluoromethanesulfonate,        bistrifluoromnethanesulfonimide, tosylate, a carboxylate, an        acetylacetonate, a carbonate, an aluminate, a borate, an        antimonate such as SbF₆ ⁻, an arsenate such as AsF₆ ⁻, a        phosphate such as PF₆ ⁻ or PO₄ ⁻, a perchlorate such as ClO₄ ⁻,        an amide such as (R″)₂N, and a phosphide such as (R″)₂P,    -   wherein said hydrocarbyl anion can be selected from the group        consisting of: a hydride; a C₁ to C₂₀ linear or branched alkyl,        haloalkyl, alkenyl, haloalkenyl, vinyl, or halovinyl; a C₅ to        C₁₂ cycloalkyl or halocycloalkyl substituted by a hydrocarbon or        unsubstituted; a C₆ to C₄₀ aryl or haloaryl substituted by a        hydrocarbon or unsubstituted; a C₆ to C₄₀ aryl or haloaryl        containing a hetero atom; a C₇ to C₁₅ aralkyl or haloaralkyl        substituted by a hydrocarbon or unsubstituted; and a C₃ to C₂₀        alkynyl or haloalkynyl,    -   said acetate and acetylacetonate are [R″C(O)O]⁻ and        [R″′C(O)CHC(O)R″″]⁻ respectively, which are anionic ligands        offering an σ-bond or π-bond, and    -   each of R″, R′″, and R″″ is hydrogen; a halogen; a C₁ to C₂₀        linear or branched alkyl, haloalkyl, alkenyl, haloalkenyl,        vinyl, or halovinyl; a C₅ to C₁₂ cycloalkyl or halocycloalkyl        substituted by a hydrocarbon or unsubstituted; a C₆ to C₄₀ aryl        or haloaryl substituted by a hydrocarbon or unsubstituted; a C₆        to C₄₀ aryl or haloaryl containing a hetero atom; a C₇ to C₁₅        aralkyl or haloaralkyl substituted by a hydrocarbon or        unsubstituted; or a C₃ to C₂₀ alkynyl or haloalkynyl.

Preferably, the compound comprising a neutral group 15 electron donorligand, a cone angle of which is at least 160°, of ii), is a compoundrepresented by the following Chemical Formula 5 or Chemical Formula 6:P(R⁵)_(3−c)[X(R⁵)_(d)]_(c)  Chemical Formula 5

In Chemical Formula 5,

-   -   X is oxygen, sulfur, silicon, or nitrogen;    -   c is an integer from 0 to 3;    -   wherein if X is oxygen or sulfur, d is 1, if X is silicon, d is        3, and if X is nitrogen, d is 2, and    -   if c is 3 and X is oxygen, two or three R⁵s may be connected        with oxygen to form a cyclic group; and if c is 0, two R⁵s may        be connected with each other to form a phosphacycle; and    -   each R⁵ is hydrogen; a C₁ to C₂₀ linear or branched alkyl,        alkoxy, allyl, alkenyl, or vinyl; a C₅ to C₁₂ cycloalkyl        substituted by a hydrocarbon or unsubstituted; a C₆ to C₄₀ aryl        substituted by a hydrocarbon or unsubstituted; a C₇ to C₁₅        aralkyl substituted by a hydrocarbon or unsubstituted; a C₃ to        C₂₀ alkynyl; a tri(C₁ to C₁₀ linear or branched alkyl)silyl; a        tri(C₁ to C₁₀ linear or branched alkoxy)silyl; a tri(C₅ to C₁₂        cycloalkyl substituted by a hydrocarbon or unsubstituted)silyl;        a tri(C₆ to C₄₀ aryl substituted by a hydrocarbon or        unsubstituted)silyl; a tri(C₆ to C₄₀ aryloxy substituted by a        hydrocarbon or unsubstituted)silyl; a tri(C₁ to C₁₀ linear or        branched alkyl)siloxy; a tri(C₅ to C₁₂ cycloalkyl substituted by        a hydrocarbon or unsubstituted)siloxy; or a tri(C₆ to C₄₀ aryl        substituted by a hydrocarbon or unsubstituted)siloxy; wherein        each functional group can be substituted by a linear or branched        haloalkyl, or a halogen.        (R⁵)₂P-(R⁶)-P(R⁵)₂  Chemical Formula 6

In Chemical Formula 6,

-   -   R⁵ is the same as defined in Chemical Formula 5; and    -   R⁶ is a C₁ to C₅ linear or branched alkyl, alkenyl, or vinyl; a        C₅ to C₁₂ cycloalkyl substituted by a hydrocarbon or        unsubstituted; a C₆ to C₂₀ aryl substituted by a hydrocarbon or        unsubstituted; or a C₇ to C₁₅ aralkyl substituted by a        hydrocarbon or unsubstituted.

Also, preferably, the salt of iii) capable of offering an anion whichcan be weakly coordinated to said transition metal of i) is a saltrepresented by the following Chemical Formula 7:[Cat]_(a)[Anion]_(b)  Chemical Formula 7

In Chemical Formula 7,

-   -   Cat is a cation selected from the group consisting of hydrogen;        a cation of a group 1 metal, a group 2 metal, or a transition        metal; and an organic group comprising said cations, to which        the neutral group 15 electron donor compound of ii) can be        bonded;    -   Anion is an anion that can be weakly coordinated to the metal M        of the compound represented by Chemical Formula 3, which is        selected from the group consisting of borate, aluminate, SbF₆ ⁻,        PF₆ ⁻, AlF₃O₃SCF₃ ⁻, SbF₅SO₃F⁻, AsF₆ ⁻, perfluoroacetate (CF₃CO₂        ⁻), perfluoropropionate (C₂F₅CO₂ ⁻), perfluorobutyrate        (CF₃CF₂CF₂CO₂ ⁻), perchlorate (ClO₄ ⁻), p-toluenesulfonate        (p-CH₃C₆H₄SO₃ ⁻), SO₃CF₃ ⁻, boratabenzene, and caborane        substituted by halogen or unsubstituted; and    -   a and b are number of cations and anions, respectively, and are        determined so that electrical neutrality is obtained.

Preferably, the cation-containing organic group in Chemical Formula 7 isselected from the group consisting of ammonium ([NH(R⁷)₃]⁺ or[N(R⁷)₄]⁺); phosphonium ([PH(R⁷)₃]⁺ or [P(R⁷)₄]⁺); carbonium([C(R⁷)₃]⁺); silyliuin ([Si(R⁷)₃]+); [Ag]⁺; [Cp2Fe]⁺; and [H(OEt₂)₂]⁺,wherein each R⁷ is a C₁ to C₂₀ linear or branched alkyl; an alkyl orsilylalkyl substituted by a halogen; a C₅ to C₁₂ cycloalkyl substitutedby a hydrocarbon or unsubstituted; a cycloalkyl or silylcycloalkylsubstituted by a halogen; a C₆ to C₄₀ aryl substituted by a hydrocarbonor unsubstituted; an aryl or silylaryl substituted by a halogen; a C₇ toC₁₅ aralkyl substituted by a hydrocarbon or unsubstituted; or an aralkylor silyl aralkyl substituted by a halogen.

Also, preferably, the borate and alumninate in Chemical Formulas 3, 4,and 7 are anions represented by the following Chemical Formula 8 orChemical Formula 9:[M′(R⁸)(R⁹)(R¹⁰)(R¹¹)]  Chemical Formula 8[M′(OR¹²)(OR¹³)(OR¹⁴)(OR¹⁵)]  Chemical Formula 9

In Chemical Formula 8 and Chemical Formula 9,

-   -   M′ is boron or aluminum; and    -   each of R⁸, R⁹, R¹⁰, R¹¹, R¹², R³, R⁴, and R¹⁵ is a halogen; a        C₁ to C₂₀ linear or branched alkyl or alkenyl substituted by a        halogen or unsubstituted; a C₅ to C₁₂ cycloalkyl substituted by        a hydrocarbon or unsubstituted; a C₆ to C₄₀ aryl substituted by        a hydrocarbon or unsubstituted; a C₇ to C₁₅ aralkyl substituted        by a hydrocarbon or unsubstituted; a C₃ to C₂₀ alkynyl; a C₃ to        C₂₀ linear or branched trialkylsiloxy; or a C₁₈ to C₄₈ linear or        branched triarylsiloxy.

The catalyst system of the present invention is a highly active catalystsystem capable of avoiding a catalytic activity decrease by an endoester group or acetyl group. It makes it easy to prepare apolycycloolefin having such polar groups as ester groups or acetylgroups.

A polycycloolefin, which is used to prepare the negative C-plate typeoptical anisotropic film of the present invention, experiences nooptical loss due to light absorption in the visible region, hasrelatively low water absorptivity, has a higher surface tension when apolar functional group is introduced than when only nonpolar functionalgroups are present, and has superior adhesivity to polyvinyl alcohol(PVA) film and metal.

In the optical anisotropic film of the present invention, it ispreferable to introduce a functional group such as an ester group oracetyl group to the norbornene-based monomer represented by ChemicalFormula 1 to increase the negative birefringence along the thicknessdirection. Other than an ester group and acetyl group, functional groupssuch as an alkoxy group, an amino group, a hydroxyl group, a carbonylgroup, and a halogen-containing group can be introduced, but thefunctional groups are not limited to the aforementioned. As seen inExamples, the refractive index and R_(th) value can be controlled bychanging the kind and content of the functional group introduced tonorbornene.

In general, to obtain a large R_(th) value, a cycloolefin having a largem of Chemical Formula 1 is introduced, the content of polar functionalgroups is increased, the length of substituents is reduced by reducingthe number of carbons present in R₁, R₂, R₃, R₄, and R₅, highly polarfunctional groups are introduced, or a cycloolefin wherein R₁ or R₂ isconnected with R₃ or R₄ to form a C₆ to C₂₄ aromatic cyclic compound isintroduced.

The negative C-plate type optical anisotropic film of the presentinvention is prepared in film or sheet form through solution casting, bydissolving said polycycloolefin in a solvent.

The film is prepared from a homopolymer of norbornene-based monomerscontaining nonpolar functional groups, a copolymer of norbornene-basedmonomers containing different nonpolar functional groups, a homopolymerof norbornene-based monomers containing polar functional groups, acopolymer of norbornene-based monomers containing different polarfunctional groups, or a copolymer of norbornene-based monomerscontaining nonpolar functional groups and norbornene-based monomerscontaining polar functional groups. Also, the film can be prepared fromblends which can be composed of one or more of these polycycloolefinpolymers.

For the organic solvent used in solution casting, one that offersappropriate viscosity when a polycycloolefin has been dissolved ispreferable. More preferably, the solvent is selected from the groupconsisting of an ether having 3 to 12 carbon atoms, a ketone having 3 to12 carbon atoms, an ester having 3 to 12 carbon atoms, a halogenatedhydrocarbon having 1 to 6 carbon atoms, and an aromatic compound. Saidether, ketone, or ester compound may have a ring structure. In addition,compounds having more than one ether, ketone, or ester functional groupsand compounds having a functional group and a halogen atom can be used.

For said ether having 3 to 12 carbon atoms, there are diisopropyl ether,dimethoxymethane, tetrahydrofuran, etc. For said ester having 3 to 12carbon atoms, there are ethyl formate, propyl formate, pentyl formate,methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate,isobutyl acetate, pentyl acetate, etc. Preferably, said halogenatedhydrocarbon has 1 to 4 carbon atoms, and more preferably one carbonatom. A preferred examples of said halogenated hydrocarbon is methylenechloride having a chlorine atom. For said aromatic compound, there arebenzene, toluene, chlorobenzene, etc.

In preparing a film through the solution casting method by dissolving apolycycloolefin in a solvent, it is preferable to add 5 to 95 wt %, morepreferably 10 to 60 wt %, of a polycycloolefin of the polymer weight ina solvent, and stir the solution at room temperature. It is preferablethat the viscosity of the solution is 100 to 20,000 cps, more preferably300 to 10,000 cps. To improve mechanical strength, heat resistance,optical resistance, and maintainability of the film, such additives as aplasticizer, an antideteriorant, a UV stabilizer, and an antistaticagent can be added.

For said plasticizer, carboxylic acid esters such as dimethyl phthalate(DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctylphthalate (DOP), diphenyl phthalate (DPP), and diethylhexyl phthalate(DEHP), or phosphoric acid esters such as triphenyl phosphate (TPP) andtricresyl phosphate (TCP) may be used. If too much low-molecular-weightplasticizer is used, it may spread to the film surface and thereforereduce the durability of the film. Therefore, the plasticizer is used inan appropriate level (e.g. 0.1 to 20 wt %). A polycycloolefin with ahigher glass transition temperature requires a larger plasticizercontent.

For said antideteriorant, it is preferable to use phenolic derivativesor aromatic amines. The antideteriorant content is determined so thatoptical properties, mechanical properties, and durability of the filmare not affected.

Examples of phenolic antideteriorants areoctadecyl-3-(4-hydroxy-3,5-di-tert-butylphenyl) propionate (Irganox 1076of Ciba-Geigy), tetrabis[methylene-3-(3,5-di-tert-butyl4-hydroxyphenyl)propionate methane (Irganox 1010 of Ciba-Geigy), 1, 3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl) benzene(Irganox 1330 of Ciba-Geigy), andtris-(3,5-di-tert-butyl-4-hydroxybenzyl)isoamine (Irganox 3114 ofCiba-Geigy).

Examples of aromatic amine antideteriorants are phenyl-α-naphtylamine,phenyl-β-naphtylamine, N,N′-diphenyl-p-phenylenediamine, andN,N′-di-β-naphtyl-p-phenylenediamine.

The antideteriorant may be used along with such peroxide decomposers asa phosphite compound or a sulfide compound. An example of the phosphiteperoxide decomposers is tris(2,4-di-tert-butylphenyl)phosphite (Irgafos168 of Ciba-Geigy), and examples of sulfide peroxide decomposers aredilauryl sulfide, dilauryl thiodipropionate, distearyl thiodipropionate,mercaptobenzothioazole, and tetramethylthiuram disulfide.

For said UV stabilizer, it is preferable to use benzophenone,salicylate, or benzotria compounds. Examples of benzophenone UVstabilizers are 2-hydroxy-4-otoxybenzophenone and2,2′-dihydroxy-4,4′-dioctoxy benzophenone; an example of salicylate UVstabilizers is p-octyl phenyl salicylate; and an example of benzotria UVstabilizers is 2-(2′-hydroxy-5′-methylphenyl) benzophenone.

For said antistatic agent, any antistatic agent miscible with thepolynorbornene solution can be used. Preferably, the antistatic agenthas a surface specific resistance equal to or lower than 10¹⁰ Ω.Non-ionic, anionic, or cationic antistatic agents can be used.

Examples of non-ionic antistatic agents are polyoxy ethylene alkylether, polyoxy ethylene alkyl phenol ether, polyoxy ethylene alkylester, polyoxy ethylene stearyl amine, and polyoxy ethylene alkyl amine.

Examples of anionic antistatic agents are sulfuric acid ester salt,alkyl allyl sulfonate, aliphatic amide sulfonate, and phosphoric acidester salt.

Examples of cationic antistatic agents are aliphatic amine salt, alkylpyridinium salt, imidazoline derivative, betaine alkyl amino derivative,sulfuric acid ester derivative, and phosphoric acid ester derivative.

Besides the aforementioned, ionic polymer compounds, such as an anionicpolymer compound disclosed in Japan Patent Publication No. Sho 49-23828;an ionene-type compound having dissociated groups in the main chain asdisclosed in Japan Patent Publication No. Sho 55-734, Japan PatentPublication No. Sho 59-14735, and Japan Patent Publication No. Sho57-18175; a cationic polymer compound disclosed in Japan PatentPublication No. Sho 53-13223; and a graft copolymer disclosed in JapanPatent Publication No. Hei 5-230161, can be used as antistatic agent.

After casting or coating the polycycloolefin solution of the presentinvention on a polished band, drum, or glass plate, the solvent is driedto obtain an optical film or sheet. The solvent drying temperature isselected depending on what solvent is used. For polished metal or glassplate, a surface temperature lower than room temperature is preferable.After the solvent is fully dried, the formed film or sheet is peeledfrom the metal or glass plate.

Such prepared optical film of the present invention is an opticallyanisotropic transparent film having a retardation value (Rut) defined byEquation 1 in the range of 30 to 1000 nm.

Preferably, when the film thickness ranges from 30 to 200 μm, theR_(th), value ranges from 30 to 1000 nm. More preferably, when the filmthickness ranges from 50 to 120 μm, the R_(th) value ranges from 50 to600 nm. Because this film is highly transparent, at least 90% of lightin the range of 400 to 800 nin is transmitted, and the phase differenceratios at two wavelengths at a given declined angle, (R₄₅₀/R₅₅₀) and(R₆₅₀/R₅₅₀), are at most 1.05 and at least 0.95, respectively.Therefore, it has flat wavelength dispersive characteristic. Here, R₄₅₀is the phase difference at 450 nm, R₅₅₀ is the phase difference atwavelength 550 nm, and R₆₅₀ is the phase difference at 650 nm. Such aflat wavelength dispersive characteristic can be altered by blending orintroduction of functional groups into the polymer, if necessary. Infact, the phase difference ratios at two wavelengths are (R₄₅₀/R₅₅₀)=1to 1.05, and (R₆₅₀/R₅₅₀)=0.95 to 1.

Since the optical film comprising a polycycloolefin of the presentinvention is optically anisotropic and has very superior adhesivity tosuch materials as polyvinyl alcohol (PVA), it can be attached to a PVApolarizing film, etc. Also, when it is treated by corona discharge, glowdischarge, flame, acid, alkali, UV radiation, or coating, its propertiessuch as transparency and anisotropy are not deteriorated.

The optical anisotropic film of the present invention has refractiveindices satisfying the relationship of the following Equation 5:n _(x) ≈n _(y) >n _(z)  Equation 5

-   -   (n_(x)=refractive index along the slow axis, n_(y)=refractive        index along the fast axis, n_(z)=refractive index along the        thickness direction)

Additionally, the optical anisotropic film comprising a polycycloolefinof the present invention can offer fine image quality at a wide viewangle and improve brightness during ON/OFF of the driving cell, whenused for a liquid crystal display. In particular, when the voltage isapplied ON or OFF state, refractive indices of the liquid crystal layersatisfy the relationship expressed by the following Equation 6, and thusenables optical compensation of the liquid crystal mode liquid crystaldisplay:n _(x) ≈n _(y) <n _(z)  Equation 6

-   -   (n_(x)=refractive index along the slow axis, n_(y)=refractive        index along the fast axis, n_(z)=refractive index along the        thickness direction)

Hereinafter, the present invention is described in more detail throughExamples and Comparative Examples. However, the following Examples areonly for the understanding of the present invention, and the presentinvention is not limited by the following Examples.

EXAMPLES Preparation Example 1 Polymerization of Norbornene CarboxylicAcid Methyl Ester

A norbornene carboxylic acid methyl ester monomer and purified toluenewere added to a polymerization reactor in a 1:1 weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 80° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid methyl ester polymer (PMeNB).

Preparation Example 2 Polymerization of Norbornene Carboxylic Acid ButylEster

A norbornene carboxylic acid butyl ester norbornene monomer and purifiedtoluene were added to a polymerization reactor in a 1:1 weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 80° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid butyl ester polymer (PBeNB).

Preparation Example 3 Copolymerization of Norbornene Carboxylic AcidButyl Ester-Norbornene Carboxylic Acid Methyl Ester (NorborneneCarboxylic Acid Butyl Ester/Norbornene Carboxylic Acid Methyl Ester=7/3)

A 3:7 molar ratio of norbornene carboxylic acid methyl ester andnorbornene carboxylic acid butyl ester were added to a polymerizationreactor as monomers. Then, purified toluene was added in a 1:1 (for thetotal monomer content) weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 80° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid butyl ester/norbornene carboxylic acid methyl ester(7:3) copolymer (PBe-7-Me-3-NB).

Preparation Example 4 Copolymerization of Norbornene Carboxylic AcidButyl Ester-Norbornene Carboxylic Acid Methyl Ester (NorborneneCarboxylic Acid Butyl Ester/Norbornene Carboxylic Acid Methyl Ester=5/5)

A 5:5 molar ratio of norbornene carboxylic acid methyl ester andnorbornene carboxylic acid butyl ester were added to a polymerizationreactor as monomers. Then, purified toluene was added in a 1:1 (for thetotal monomer content) weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 80° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid methyl ester/norbornene carboxylic acid butyl ester(5:5) copolymer (PBe-5-Me-5-NB).

Preparation Example 5 Copolymerization of Norbornene Carboxylic AcidButyl Ester-Norbornene Carboxylic Acid Methyl Ester (NorborneneCarboxylic Acid Butyl Ester/Norbornene Carboxylic Acid Methyl Ester=3/7)

A 3:7 molar ratio of norbornene carboxylic acid butyl ester andnorbornene carboxylic acid methyl ester were added to a polymerizationreactor as monomers. Then, purified toluene was added in a 1:1 (for thetotal monomer content) weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 80° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid butyl ester/norbornene carboxylic acid methyl ester(3:7) copolymer (PBe-3-Me-7-NB).

Preparation Example 6 Copolymerization of Norbornene Carboxylic AcidMethyl Ester-Butyl Norbornene (Norbornene Carboxylic Acid MethylEster/Butyl Norbornene=317)

A 3:7 molar ratio of norbornene carboxylic acid methyl ester and butylnorbornene were added to a polymerization reactor as monomers. Then,purified toluene was added in a 1:1 (for the total monomer content)weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 90° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid methyl ester/butyl norbornene (3:7) copolymer(PBu-7-Me-3-NB).

Preparation Example 7 Copolymerization of Norbornene Carboxylic AcidMethyl Ester-Butyl Norbornene (Norbornene Carboxylic Acid MethylEster/Butyl Norbornene=5/5)

A 5:5 molar ratio of norbornene carboxylic acid methyl ester and butylnorbornene were added to a polymerization reactor as monomers. Then,purified toluene was added in a 1:1 (for the total monomer content)weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 18 hours whilestirring at 90° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid methyl ester/butyl norbornene (5:5) copolymer(PBu-5-Me-5-NB).

Preparation Example 8 Copolymerization of Norbornene Carboxylic AcidMethyl Ester-Butyl Norbornene (Norbornene Carboxylic Acid MethylEster/Butyl Norbornene=7/3)

A 7:3 molar ratio of norbornene carboxylic acid methyl ester and butylnorbornene were added to a polymerization reactor as monomers. Then,purified toluene was added in a 1:1 (for the total monomer content)weight ratio.

0.01 mol % (for the monomer content) of Pd(acac)₂ dissolved in tolueneand 0.01 mol % (for the monomer content) of tricyclohexylphosphine, ascatalysts, and 0.02 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 20 hours whilestirring at 90° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 65° C. to obtain a norbornenecarboxylic acid methyl ester/butyl norbornene (7:3) copolymer(PBu-3-Me-7-NB).

Preparation Example 9 Polymerization of Butyl Norbornene

A butyl norbornene monomer and purified toluene were added to apolymerization reactor in a 1:1 weight ratio.

0.025 mol % (for the monomer content) of Ni(ethylhexanoate) dissolved inmethylene chloride, as a catalyst, and 0.225 mol % (for the monomercontent) of tris(pentafluorophenyl)boron and 0.25 mol % (for the monomercontent) of triethylaluminum dissolved in toluene, as cocatalysts, wereadded to the reactor. Reaction was carried out for 20 hours whilestirring at room temperature.

After the reaction was completed, the reaction mixture was added to amethylene chloride solution after dissolving a small amount ofhydroxyquinoline therein. After stirring for 18 hours, the solution wasadded to excess ethanol to obtain a white copolymer precipitate. Theprecipitate was filtered with a glass funnel, and the collectedcopolymer was dried in a vacuum oven for 24 hours at 80° C. to obtain abutyl norbornene polymer (PBuNB).

Preparation Example 10 Polymerization of Octyl Norbornene-NorborneneCopolymer (Octyl Norbornene/Norbornene=8/2)

An 8:2 molar ratio of octyl norbornene and norbornene were added to apolymerization reactor as monomers. Then, purified toluene was added ina 1:1 (for the total monomer content) weight ratio.

0.025 mol % (for the monomer content) of Ni(ethylhexanoate) dissolved intoluene, as a catalyst, and 0.225 mol % (for the monomer content) oftris(pentafluorophenyl)boron and 0.25 mol % (for the monomer content) oftriethylaluminum dissolved in toluene, as cocatalysts, were added to thereactor. Reaction was carried out for 20 hours while stirring at roomtemperature.

After the reaction was completed, the reaction mixture was added to amethylene chloride solution after dissolving a small amount ofhydroxyquinoline therein. After stirring for 12 hours, the solution wasadded to excess ethanol to obtain a white copolymer precipitate. Theprecipitate was filtered with a glass funnel, and the collectedcopolymer was dried in a vacuum oven for 24 hours at 80° C. to obtain aoctylnorbornene/norbornene (8:2) copolymer (POc-8-NB-2).

Preparation Example 11 Polymerization of Decyl Norbornene-NorborneneCopolymer (Decyl Norbornene/Norbornene=7:3)

A 7:3 molar ratio of decyl norbornene and norbornene were added to apolymerization reactor as monomers. Then, purified toluene was added ina 1:1 (for the total monomer content) weight ratio.

0.025 mol % (for the monomer content) of Ni(ethylhexanoate) dissolved intoluene, as a catalyst, and 0.225 mol % (for the monomer content) oftris(pentafluorophenyl)boron and 0.25 mol % (for the monomer content) oftriethylaluminum dissolved in toluene, as cocatalysts, were added to thereactor. Reaction was carried out for 17 hours while stirring at roomtemperature.

After the reaction was completed, the reaction mixture was added to amethylene chloride solution after dissolving a small amount ofhydroxyquinoline therein. After stirring for 12 hours, the solution wasadded to excess ethanol to obtain a white copolymer precipitate. Theprecipitate was filtered with a glass funnel, and the collectedcopolymer was dried in a vacuum oven for 24 hours at 80° C. to obtain adecylnorbornene/norbornene (7:3) copolymer (PDe-7-NB-3).

Preparation Example 12 Polymerization of Triethoxy Silyl Norbornene

A triethoxy silyl norbornene monomer and purified toluene were added toa polymerization reactor in a 1:1 weight ratio.

0.02 mol % (for the monomer content) of Ni(ethylhexanoate) dissolved intoluene, as a catalyst, and 0.18 mol % (for the monomer content) oftris(pentafluorophenyl)boron and 0.2 mol % (for the monomer content) oftriethylaluminum dissolved in toluene, as cocatalysts, were added to thereactor. Reaction was carried out for 18 hours while stirring at roomtemperature.

After the reaction was completed, the reaction mixture was added to amethylene chloride solution after dissolving a small amount ofhydroxyquinoline therein. After stirring for 12 hours, the solution wasadded to excess ethanol to obtain a white copolymer precipitate. Theprecipitate was filtered with a glass funnel, and the collectedcopolymer was dried in a vacuum oven for 24 hours at 70° C. to obtain atriethoxy silyl norbornene polymer (PTesNB).

Preparation Example 13 Polymerization of Acetate Norbornene

An acetate norbornene monomer and purified toluene were added to apolymerization reactor in a 1:1 weight ratio.

0.03 mol % (for the monomer content) of Pd(acac)₂ and 0.03 mol % (forthe monomer content) of tricyclohexylphosphine dissolved in toluene, ascatalysts, and 0.06 mol % (for the monomer content) of dimethylaniliniumtetrakis(pentafluorophenyl)borate dissolved in CH₂Cl₂, as a cocatalyst,were added to the reactor. Reaction was carried out for 17 hours whilestirring at 80° C.

After the reaction was completed, the reaction mixture was added toexcess ethanol to obtain a white copolymer precipitate. The precipitatewas filtered with a glass funnel, and the collected copolymer was driedin a vacuum oven for 24 hours at 80° C. to a obtain norbornene acetatepolymer (PAcNB).

Examples 1 to 14

(Preparation of Film)

Each polymer obtained in Preparation Examples 1 to 13 was prepared intoa solution having compositions of Table 1 below. Each coating solutionwas cast on a glass plate using a knife coater or a bar coater. Theglass plate was dried at room temperature for 1 hour, and then undernitrogen at 100° C. for 18 hours. After keeping at −10° C. for 10seconds, a film formed on the glass plate was peeled with a knife toobtain a transparent film with a thickness deviation being below 2%.Thickness and optical transmittivity at 400 to 800 nm of each film arealso shown in Table 1. TABLE 1 Film solution Physical propertiescomposition Optical (parts by weight) Thickness transmittivityClassification Polymer Additives Solvent (μm) (%) Example 1 PMeNB — THF,560 114 92 (Preparation Example 1), 100 Example 2 PBeNB — MC, 360; 12092 (Preparation Toluene, 200 Example 2), 100 Example 3 PBe-7-Me-3-NB —Toluene 560 103 91 (Preparation Example 3), 100 Example 4 PBe-7-Me-3-NBTPP, 5; MC, 360; 105 91 (Preparation Irganox 1,010, 0.3 Toluene, 200Example 3), 100 Example 5 PBe-5-Me-5-NB — Toluene, 560 110 92(Preparation Example 4), 100 Example 6 PBe-3-Me-7-NB — Toluene, 480 97(Preparation Example 5), 100 Example 7 PBu-7-Me-3-NB — Toluene, 560 9892 (Preparation Example 6), 100 Example 8 PBu-5-Me-5-NB — Toluene, 560105 92 (Preparation Example 7), 100 Example 9 PBu-3-Me-7-NB — Toluene,730 101 91 (Preparation Example 8), 100 Example 10 PBuNB — Toluene, 40099 91 (Preparation Example 9), 100 Example 11 POc-8-NB-2 — Toluene, 400105 91 (Preparation Example 10), 100 Example 12 PDe-7-NB-3 — Toluene,400 107 91 (Preparation Example 11), 100 Example 13 PtesNB — Toluene,350 106 92 (Preparation Example 12), 100 Example 14 PacNB — THF, 500; 9591 (Preparation Toluene, 300 Example 13), 100

In Table 1, TPP stands for phosphoric acid ester of triphenyl phosphate;THF stands for tetrahydrofuran; and MC stands for methylenechloride.

(Optical Anisotropy Measurement)

The refractive index (n) of each transparent film of Examples 1 to 14was measured using an Abbe refractometer, and the in-plane phasedifference value (R_(e)) was measured with an automatic birefringencemeter (KOBRA-21 ADH; Wang Ja). The phase difference value (R_(θ)) wasmeasured when the angle between the incident light and the film surfacewas 50°, and the phase difference (R_(th)) along the film thicknessdirection and in-plane x-axis was calculated by the following Equation3: $\begin{matrix}{R_{th} = \frac{R_{\theta} \times \cos\quad\theta_{f}}{\sin^{2}\theta_{f}}} & {{Equation}\quad 3}\end{matrix}$

The refractive index difference [(n_(x)−n_(y)) and (n_(y)−n_(z))] wascalculated by dividing R_(e) and R_(th) by film thickness. Therefractive index difference, R_(θ), and R_(th) values of eachtransparent film are shown in the following Table 2. TABLE 2 n(refractive R_(th) Classification Polymer index) (n_(x) − n_(y)) × 10³(nm/μm) (n_(y) − n_(z)) × 10³ Example 1 PMeNB 1.52 0.008 5.78 5.78(Preparation Example 1) Example 2 PbeNB 1.50 0.009 2.13 2.13(Preparation Example 2) Example 3 PBe-7-Me-3-NB 1.51 0.012 3.29 3.29(Preparation Example 3) Example 4 PBe-7-Me-3-NB 1.51 0.014 2.79 2.79(Preparation Example 3) Example 5 PBe-5-Me-5-NB 1.51 0.013 3.59 3.59(Preparation Example 4) Example 6 PBe-3-Me-7-NB 1.52 0.020 4.35 4.35(Preparation Example 5) Example 7 PBu-7-Me-3-NB 1.52 0.015 3.63 3.63(Preparation Example 6) Example 8 PBu-5-Me-5-NB 1.51 0.007 3.98 3.98(Preparation Example 7) Example 9 PBu-5-Me-5-NB 1.51 0.009 4.25 4.25(Preparation Example 8) Example 10 PbuNB 1.50 0.008 1.44 1.44(Preparation Example 9) Example 11 POc-8-NB-2 1.50 0.013 1.28 1.28(Preparation Example 10) Example 12 PDe-7-NB-3 1.50 0.019 0.79 0.79(Preparation Example 11) Example 13 PtesNB 1.52 0.008 1.47 1.47(Preparation Example 12) Example 14 PacNB 1.52 0.015 5.46 5.46(Preparation Example 13)

When R_(θ) was measured after putting the films on a triacetatecellulose film (n_(y)>n_(z)), R_(θ) values of all cycloolefin filmsincreased. This shows that the R_(th) of cycloolefin films results fromnegative birefringence along the thickness direction (n_(y)>n_(z)).

Examples 15 to 18

To identify the effect of drying condition on the R_(th) value, filmswere prepared under a variety of drying conditions as shown in Table 3below. Drying conditions were at 100° C. for 18 hours while: injectingnitrogen gas at 10 mg/min into drying oven; drying under vacuum; anddrying in the air. Other film preparation conditions were the same as inExamples 3 and 5. The R_(th) measurement result showed that the dryingcondition does not substantially affect the R_(th) value. TABLE 3 DryingR_(th) Classification Polymer method Pre-drying Post-drying (nm/μm)Example 15 PBe-5-Me-5-NB Vacuum Room 100° C., 18 3.56 (Preparationtemperature, hours Example 4) 1 hour Example 16 PBe-5-Me-5-NB NitrogenRoom 100° C., 18 3.58 (Preparation flow temperature, hours Example 4) 1hour Example 17 PBe-7-Me-3-NB Vacuum Room 100° C., 18 3.33 (Preparationtemperature, hours Example 3) 1 hour Example 18 PBe-7-Me-3-NB Air Room100° C., 18 3.31 (Preparation temperature, hours Example 3) 1 hour

Example 19 Wavelength Dispersive Characteristic of Phase Difference

The in-plane phase difference value (R_(e)) was measured with anautomatic birefringence meter (KOBRA-21 ADH; Wang Ja). The phasedifference value (R_(θ)) was measured when the angle between theincident light and the film surface was 50°, and the phase difference(R_(th)) along the film thickness direction and in-plane x-axis wascalculated by the aforementioned Equation 3.

For each transparent film prepared in Examples 2 to 13, R_(θ) values fordifferent wavelengths (A=479.4 nm, 548 nm, 629 nin, 747.7 nm) weremeasured at an incident angle of 50° using an automatic birefringencemeter (KOBRA-21 ADH; Wang Ja). The ratio to the R_(θ) value at standardwavelength (λ₀=550 nm), R₅₀(λ)/R₅₀(λ₀), was calculated. The results areshown in Table 4 below. TABLE 4 R₅₀(479.4)/ R₅₀(548)/ R₅₀(629)/R₅₀(747.7)/ Classification Polymer R₅₀(λ₀) R₅₀(λ₀) R₅₀(λ₀) R₅₀(λ₀)Example 2 PbeNB 1.007 1.000 0.998 0.987 (Preparation Example 2) Example3 PBe-7-Me-3-NB 1.007 1.000 1.000 0.983 (Preparation Example 3) Example4 PBe-7-Me-3-NB 1.010 1.000 0.997 0.965 (Preparation Example 3) Example5 PBe-5-Me-5-NB 1.008 1.000 1.000 0.992 (Preparation Example 4) Example6 PBe-3-Me-7-NB 1.007 1.000 0.997 0.968 (Preparation Example 5) Example7 PBu-7-Me-3-NB 1.010 1.000 0.993 0.983 (Preparation Example 6) Example8 PBu-5-Me-5-NB 1.005 1.000 0.997 0.972 (Preparation Example 7) Example9 PBu-3-Me-7-NB 1.008 1.000 0.998 0.975 (Preparation Example 8) Example10 PbuNB 1.014 1.000 1.000 0.970 (Preparation Example 9) Example 11POc-8-NB-2 1.004 1.000 0.981 0.967 (Preparation Example 10) Example 12PDe-7-NB-3 1.014 1.001 0.986 0.980 (Preparation Example 11) Example 13PtesNB 1.017 1.000 0.974 0.969 (Preparation Example 12)

Example 18 Water Absorptivity

Three specimens of triacetate cellulose film (thickness=80 μm) and PBeNBfilm of Example 2 (thickness=120 μm), each measuring 5×5 cm; wereprepared. Each specimen was immersed in water at room temperature. After24 hours and 120 hours, the specimens were taken out. Water on thespecimen surface was wiped and the weight difference was measured. Theresults are shown in Table 5 below. TABLE 5 Water absorptivityClassification of PBeNB (%) Water absorptivity of TAC (%) After 24 hours0.17 ± 0.02 1.23 ± 0.12 After 120 0.17 ± 0.02 1.23 ± 0.12 hours

Example 19 Effect of Additives on Heat Resistance

The polybutyl ester-methyl ester (7:3) copolymer film of Example 3 andthe film of Example 4, which further comprises 5 wt % of triphenylphosphate and 0.3 wt % of Irganox 1010 as additives, were kept at 150°C. for 3 hours, and then optical transmittivity was measured.

The polybutyl ester-methyl ester (7:3) copolymer film of Example 3showed an optical transmittivity of 89% in the range from 400 to 800 nm.The polybutyl ester-methyl ester film of Example 4 showed an opticaltransmittivity of 91%. There was no significant difference in mechanicalproperties.

Example 20 Surface Treatment and Lamination with PVA Polarizing Film

For the polybutyl ester norbornene film of Example 2, contact angle wasmeasured to calculate surface tension from the following Equations 7 and8 (Wu, S. J. Polym. Sci. C Vol 34, p19, 1971):γ_(S)=γ_(SL)+γ_(LI)·COSθ  Equation 7 $\begin{matrix}{\gamma_{SL} = {\gamma_{S} + \gamma_{LV} - {4\left( {\frac{\gamma_{LV}^{d}\gamma_{S}^{d}}{\gamma_{LV}^{d} + \gamma_{S}^{d}} + \frac{\gamma_{LV}^{p}\gamma_{S}^{p}}{\gamma_{LV}^{p} + \gamma_{S}^{p}}} \right)}}} & {{Equation}\quad 8}\end{matrix}$

In Equations 7 and 8,

-   -   γ_(S) is surface tension of the film, γ_(LV) is surface tension        of the liquid, γ_(SL) is interfacial tension of the film and        liquid, θ is the contact angle, γ^(d) is the dispersion term of        surface tension, and γ^(p) is the polar term of surface tension.

When water (γ^(d)=44.1, γ^(p)=6.7 mN/m) was used the contact angle was74.3°, and when diiodomethane (γ^(d)=22.1, γ^(p)=50.7 mN/m) was used itwas 33.5°. From these values, the surface tension was calculated to be49.5 mN/m.

The polybutyl ester norbornene film was corona treated at 6 m/min ofline speed 3 times, and the contact angle was measured again. Thecontact angle was 20.7° for water and 22° for diiodomethane. The surfacetension was calculated to be 76.9 mN/m.

Within 30 minutes of corona treatment, the film was roll-laminated on asufficiently dried PVA (polyvinylalcohol) polarizing film using a 10 wt% PVA aqueous solution, and dried for 10 minutes at 80′. The PVApolarizing film had superior adhesivity.

The negative C-plate type optical anisotropic film comprising apolycycloolefin of the present invention can be used for opticalcompensation films of a variety of LCD (liquid crystal display) modesbecause the refractive index along the thickness direction can becontrolled by the kind and amount of functional groups.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. A negative C-plate type optical anisotropic film comprising apolycycloolefin.
 2. The optical anisotropic film according to claim 1,which has a retardation value (R_(th)), defined by the followingEquation 1, of 30 to 1000 nm when the film thickness is 30 to 200 μm:R _(th)=Δ(n _(y) −n _(z))×d  Equation 1 wherein n_(y) is the in-planerefractive index along the transverse direction or along the fast axismeasured at a wavelength of 550 nm; n_(z) is the refractive index alongthe thickness direction measured at a wavelength of 550 nm; and d is thefilm thickness.
 3. The optical anisotropic film according to claim 1,wherein said polycycloolefin is: i) a homopolymer of compoundsrepresented by the following Chemical Formula 1; or ii) a copolymer oftwo or more different compounds represented by the following ChemicalFormula 1:

wherein m is an integer from 0 to 4; R₁, R₂, R₃, and R₄ are,independently or simultaneously, hydrogen; a halogen; a C, to C₂₀ linearor branched alkyl, alkenyl, or vinyl; a C₄ to C₁₂ cycloalkyl substitutedby a hydrocarbon or unsubstituted; a C₆ to C₄₀ aryl substituted by ahydrocarbon or unsubstituted; a C₇ to C₁₅ aralkyl substituted by ahydrocarbon or unsubstituted; C₃ to C₂₀ alkynyl; a C₁ to C₂₀ linear orbranched haloalkyl, haloalkenyl or halovinyl; a C₅ to C₁₂ halocycloalkylsubstituted by a hydrocarbon or unsubstituted; a C₆ to C₄₀ haloarylsubstituted by a hydrocarbon or unsubstituted; a C₇ to C₁₅ haloaralkylsubstituted by a hydrocarbon or unsubstituted; a C₃ to C₂₀ haloalkynyl;or a non-hydrocarbonaceous polar group containing at least one ofoxygen, nitrogen, phosphorus, sulfur, silicon, or boron; and if R₁, R₂,R₃, and R₄ are not hydrogen, a halogen, or a polar functional group, R.and R₂, or R₃ and R₄ may be connected to each other to form a C₁ to C₁₀alkylidene group, or R, or R₂ may be connected with R₃ or R₄ to form aC₄ to C₁₂ saturated or unsaturated cyclic group, or a C₆ to C₂₄ aromaticcyclic compound.
 4. The optical anisotropic film according to claim 3,wherein said non-hydrocarbonaceous polar group of Chemical Formula 1 isselected from the group consisting of:

wherein each R₅ is a C₁ to C₂₀ linear or branched alkyl, haloalkyl,alkenyl, haloalkenyl, vinyl, or halovinyl; a C₄ to C₁₂ cycloalkyl orhalocycloalkyl substituted by a hydrocarbon or unsubstituted; a C₆ toC₄₀ aryl or haloaryl substituted by a hydrocarbon or unsubstituted; a C₇to C₁₅ aralkyl or haloaralkyl substituted by a hydrocarbon orunsubstituted; or a C₃ to C₂₀ alkynyl or haloalkynyl; each of R₆, R₇,and R₈ is hydrogen, a halogen, a C₁ to C₂₀ linear or branched alkyl,haloalkyl, alkenyl, haloalkenyl, vinyl, halovinyl, alkoxy, haloalkoxy,carbonyloxy, or halocarbonyloxy; a C₄ to C₁₂ cycloalkyl orhalocycloalkyl substituted by a hydrocarbon or unsubstituted; a C₆ toC₄₀ aryl, haloaryl, aryloxy or haloaryloxy substituted by a hydrocarbonor unsubstituted; a C₇ to C₁₅ aralkyl or haloaralkyl; or a C₃ to C₂₀alkynyl or haloalkynyl substituted by a hydrocarbon or unsubstituted;and p is an integer from 1 to
 10. 5. The optical anisotropic filmaccording to claim 1, wherein said polycycloolefin is an olefinicaddition polymer having nonpolar functional groups.
 6. The opticalanisotropic film according to claim 1, wherein said polycycloolefin isan olefinic addition polymer having polar functional groups.
 7. Theoptical anisotropic film according to claim 1, wherein saidpolycycloolefin is a homopolymer of norbornene-based monomers havingpolar functional groups or a copolymer of norbornene-based monomershaving different polar functional groups.
 8. The optical anisotropicfilm according to claim 1, wherein said polycycloolefin is a copolymerof norbornene-based monomers having nonpolar functional groups andnorbornene-based monomers having polar functional groups.
 9. The opticalanisotropic film according to claim 1, wherein said film comprisesblends composed of one or more addition polymerized polycycloolefinpolymers.
 10. The optical anisotropic film according to claim 1, whereinsaid polycycloolefin is prepared by addition polymerization ofnorbornene-based monomers in the presence of a group 10 transition metalcatalyst.
 11. The optical anisotropic film according to claim 1, whereinsaid polycycloolefin is prepared by a method comprising a step ofcontacting norbornene-based monomers having polar functional groups witha catalyst system comprising: i) a group 10 transition metal compound,as a catalyst; ii) an organic compound comprising a neutral group 15electron donor ligand having lone pair electrons and thus capable ofacting as an electron donor, as a cocatalyst; and iii) a salt comprisinga group 13 element capable of offering an anion which can be weaklycoordinated to said transition metal, as a cocatalyst.
 12. The opticalanisotropic film comprising a polycycloolefin having ester groups oracetyl groups according to claim 1, wherein said polycycloolefin isprepared by a method comprising a step of contacting norbornene-basedmonomers having ester groups or acetyl groups with a catalyst systemcomprising: i) a group 10 transition metal compound; ii) a compoundcomprising a neutral group 15 electron donor ligand, a cone angle ofwhich is at least 160°; and iii) a salt capable of offering an anionwhich can be weakly coordinated to said transition metal of i).
 13. Theoptical anisotropic film according to claim 1, which is prepared by thesolution casting method comprising a step of dissolving apolycycloolefin in a solvent and casting the solution into a film. 14.The optical anisotropic film according to claim 1, which is surfacetreated by one or more surface treatment methods selected from the groupconsisting of corona discharge, glow discharge, flame, acid, alkali, UVradiation, and coating.
 15. An optically anisotropic transparent film,with a retardation value (R_(th)) defined by the following Equation 1ranging from 30 to 1000 nm, phase difference ratios at two wavelengthsat a given declined angle being (R₄₅₀/R₅₅₀)=1 to 1.05 and(R₆₅₀/R₅₅₀)=0.95 to 1: wherein R₄₅₀ is the phase difference at awavelength of 450 nm, R₅₅₀ is the phase difference at a wavelength of550 nm, and R₆₅₀ is the phase difference at a wavelength of 650 nm:R _(th)=Δ(n _(y) −n _(z))×d  Equation 1 wherein n_(y) is the in-planerefractive index along the fast axis measured at a wavelength of 550 nm;n_(z) is the refractive index along the thickness direction measured ata wavelength of 550 nm; and d is the film thickness.
 16. The opticallyanisotropic transparent film according to claim 15, which has opticaltransmittivity in the range from 400 to 800 nm of at least 90%.
 17. Theoptically anisotropic transparent film according to claim 15, whichcomprises a polycycloolefin.
 18. An optical anisotropic compensationfilm for a liquid crystal display comprising a polycycloolefin.
 19. Theoptical anisotropic compensation film according to claim 18, which has aretardation value (R_(th)), defined by the following Equation 1, of 30to 1000 nm when the film thickness is 30 to 200 μm:R _(th)=Δ(n _(y) −n _(z))×d  Equation 1 wherein n_(y) is the in-planerefractive index along the fast axis measured at a wavelength of 550 nm;n_(z) is the refractive index along the thickness direction measured ata wavelength of 550 nm; and d is the film thickness.
 20. The opticalanisotropic compensation film according to claim 18, refractive indicesof which satisfy the following Equation 5:n _(x) ≈n _(y) >n _(z)  Equation 5 wherein n_(x)=in-plane refractiveindex along the slow axis; n_(y)=refractive index along the fast axis;and n_(z)=refractive index along the thickness direction.
 21. A methodfor preparing an optical anisotropic film comprising the steps of: a)addition polymerizing norbornene-based monomers to prepare anorbornene-based addition polymer; b) dissolving said norbornene-basedaddition polymer in a solvent to prepare a norbornene-based additionpolymer solution; and c) coating or casting said norbornene-basedaddition polymer solution on a plate and drying the same.
 22. The methodfor preparing an optical anisotropic film according to claim 21, whichfurther comprises a step of surface treating the film obtained bycasting with corona discharge, glow discharge, flame, acid, alkali, UVradiation, or coating.
 23. The method for preparing an opticalanisotropic film according to claim 21, wherein refractive indices ofsaid film satisfy the following Equation 5:n _(x)(n _(y) >n _(z)  Equation 5 wherein nx=in-plane refractive indexalong the slow axis; ny=refractive index along the fast axis; andnz=refractive index along the thickness direction.
 24. The method forpreparing an optical anisotropic film according to claim 21, whereinsaid solution of step b) further comprises one or more additivesselected from the group consisting of a plasticizer, an antideteriorant,a UV stabilizer, and an antistatic agent.
 25. The method for preparingan optical anisotropic film according to claim 21, wherein said solutionof step b) further comprises one or more materials selected from thegroup consisting of an ether having 3 to 12 carbon atoms, a ketonehaving 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, ahalogenated hydrocarbon having 1 to 6 carbon atoms, and an aromaticcompound.
 26. A liquid crystal display comprising the opticalanisotropic film of claim
 1. 27. The liquid crystal display according toclaim 26, wherein refractive indices of the liquid crystal layer satisfythe following Equation 6 when the voltage is applied ON or OFF state:n _(x) ≈n _(y) <n _(z)  Equation 6 wherein n_(x)=in-plane refractiveindex along the slow axis; n_(y)=refractive index along the fast axis;and n_(z)=refractive index along the thickness direction.